Web guide rolls serve to conduct a material web, for instance of paper, cardboard, plastic, metal, textile or similar, optionally with controllable or regulatable tension, from one place in a mechanical plant to the next where further processing of the material web is to be undertaken, for instance by pressing, stamping, printing, rolling, smoothing, dewatering, coating, coiling or similar.
The exact transfer of the material web by means of the web guide roll is problematic, especially for high web speeds, since an air cushion forms between the outer surface of the web guide roll and the material web, the material web then begins to float on this air cushion and performs uncontrolled movements in the lateral direction so that lateral guidance of the material web is no longer achieved.
In order to remedy this problem, position measuring devices for the edges of the web and regulation devices for the positional displacement of the web guide rolls are provided, for instance in accordance with DE 25 40 923 or DE 39 13 601. These are not only involved and complicated but also function with a certain time lag so that the speed of the web is thus upwardly limited.
In order to avoid this, it was proposed to use a lathe or mill to machine peripheral grooves into the outer surface of a tubular steel or aluminium roll, which, when suitably dimensioned (for instance with a depth of several tenths of millimetres), provides good guidance of the material web and prevents lateral divergence, even for higher web or roll rotational speeds. However, the high mass forces of such rolls are disturbing.
Press rolls serve for the dewatering of fiber webs and are mainly provided with peripheral grooves. When realised as a metal roll, mass and related oscillation problems also occur. These oscillations can be substantially responsible for a shortening of the life of the dewatering felt also fed through the press gap.
To avoid such high mass forces it was proposed to manufacture the roll tube from a lighter material, for instance from a fiber-reinforced plastic which has, however, only a low surface hardness. Therefore, as a result of abrasion of the grooves, rapid wear occurs so that the operational life of such web guide rolls is often inadequate.